it crush every time you try to make a slab form a surfance that has hole in it . it seems like blast code has problem with such surfances ... the way i ve over steped this problem is that ive made two planes , cut only half of the circle on side of each one put them together so it looks like there is a hole in one surfance , and aded two control surf and two slabs ... it works in terms of of technic but i dont know if that gonna work for your specyfic demolition .
all the best mate - if you find a way to overcome this "bug" ( im guessing it is a bug for now but maybe something that we overlooked ) let me know please.